立方差公式因为x^3-y^3=(x-y)(x^2+xy+y^2) x^3-y^3=1+3xy所以1+3xy=(x-y)(x^2+xy+y^2)x-y = (1+3xy)/(x^2+xy+y^2) =(1+3xy)/[(x-y)^2+3xy]设x-y=A则上式可化为:A=(1+3xy)/[A^2+3xy]1+3xy=A3+A*3xy所以 A=1...